If you forgot your password, just go to the login page. Under the login button, you will find the "forgot your password?" button. Click on it. Type in your email address, and you will receive an email including further guidance to request a new password.
If you only want to change your password, please visit the User Profile page. On the main menu, go down to your name and click on the Pen Icon ✏️. You will be able to change your password by entering both your old and new passwords.